Conventionally, there has been an EGR device that recirculates exhaust gas of an internal combustion engine toward an intake side. The EGR device has a valve device to selectively open and close a passage for an exhaust gas (hereinafter, referred to as an “EGR gas”).
Such a valve device may include, for example, a housing, a shaft, a butterfly valve, and a sealing member.
The housing has a passage with a circular cross-section, and the shaft is rotatably supported by the housing.
The butterfly valve has a disk shape and defines a groove formed around an outer circumferential surface. The groove is recessed from the outer circumferential surface radially inward of the butterfly valve. The butterfly valve is fixed to the shaft and is housed in the passage. The sealing member is formed into an annular shape and fit in the groove. The sealing member has an inner circumferential surface that defines a clearance α between the inner circumferential surface and a bottom of the groove along a radial direction of the butterfly valve. The sealing member is configured to seal between the outer circumferential surface of the butterfly valve and an inner wall of the passage, when the passage is closed by the butterfly valve, by being elastically deformed to have at least a portion of the outer circumferential surface of the sealing member come into contact with the inner wall of the passage (see Patent Literature JP2005-233063A).
In such a valve device, a clearance β is intentionally formed in the groove along a thickness direction of the butterfly valve in addition to the clearance α in consideration of the difference between linear expansion coefficients of the housing, the valve body, and the sealing member that arises from their material differences. However, the clearances α and β may allow the sealing member to be angled relative to an ideal position, when the passage is closed, due to dimensional errors of each component or errors arising during assembling process. As a result, spaces are formed around the outer circumferential surface of the sealing member.
Especially, when the valve device is used for the EGR device, the housing, the butterfly valve, and the sealing member may significantly change in their volumes due to a drastic temperature change at the passage between high temperature of the exhaust gas and low temperature of the outside air at a cold area. Therefore, it is necessary to make the clearances α, β larger when the valve device is used for the EGR device. As a result, the above-described angle of the sealing member would increase, and the spaces would become larger.
In view of the above, it is an objective of the present disclosure to provide a valve device having a butterfly valve and a sealing member disposed in a groove around an outer circumferential surface of the sealing member, wherein spaces are prevented from forming even if a sealing member is tilted when a passage is closed.